This application claims the benefit of Korean Application No. 67676/1997, filed Dec. 11, 1997, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus and method for controlling power supplied to a laser diode, and more particularly, relates to an apparatus and method for controlling power of a laser diode used for optical recording media in which diode power is controlled in parallel to independently control power levels required for recording onto optical recording media so that laser diode power can be stably controlled with respect to reading information from and recording information onto the optical recording media.
2. Description of the Related Art
Recording media having a high recording capacity are required in the present information and multimedia age. An optical recording medium such as a digital video diskread only memory(DVD-ROM) is used as a recording medium having such high capacity. The performance of high capacity recording media is determined by controlling power of the laser diode to an utmost condition.
The apparatus and operation for controlling laser diode power, used for the current optical recording media, will be described hereinafter with reference to FIG. 1.
As shown in FIG. 1, the apparatus for controlling laser diode power includes: an interface unit 10 for controlling an interface with an external processor; a power level decoding unit 20, enabled by an enable signal from the interface unit 10, for executing decoding by receiving an address relating to one of the optical recording media from the interface unit 10, multiplexing the data corresponding to the target power level, and outputting the same; a power level control unit 30 for receiving an input/output command from the interface unit 10, receiving the data corresponding to the power level from the power level decoding unit 20 and converting the power level; a pulse generating unit 40 for generating a pulse having a predetermined form based on input data from the interface unit 10; an automatic diode power control unit 50 for maintaining an output level of the diode by converting the data corresponding to the power level from the power level decoding unit 20 into analog data; a laser diode driving unit for generating a laser diode driving signal based on a signal from the automatic diode power control unit 50 and a pulse outputted from the pulse generating unit 40; a laser diode LD1 having an anode which receives the driving signal from the laser diode driving unit 60 and a cathode which is grounded; a photo diode PD1, which is driven by the laser diode, having an anode connected to the power VCC and which outputs the output control signal of the laser diode via a cathode to the automatic diode power control unit 50; and a clock oscillating unit 70 for generating a clock for operation of the power level control unit 30.
The interface unit 10 is controlled by commands, transmitted from the external processor. The power level decoding unit 20 is enabled by an enable signal outputted from the interface unit 10 and receives the power level of the target laser diode from the interface unit 10, executes demultiplexing, with a register, and outputs the power level as digital data to the automatic diode power control unit 50. The automatic diode power control unit 50 receives the data corresponding to the power level of the laser diode, executes analog/digital converting and outputs a signal corresponding to the difference of power levels between the signal input from the cathode of the photo diode PD1 and the power level, input from the power level decoding unit. The pulse generating unit 40 generates a pulse of a predetermined type based on input data from the interface unit 10. The laser diode driving unit 60 drives the laser diode LD 1 by using the pulse, generated from the pulse generating unit 40, and the signal, generated from the automatic diode power control unit 50.
In the mean time, the power level control unit 30 receives the main clock from the clock oscillating unit 70, divides and outputs the clock to the pulse generating unit 40. The power level control unit 30 receives the data corresponding to the power level from the power level decoding unit 20 when an input/output command is received from the interface unit 10, and converts the data and outputs a signal to the automatic diode power control unit 50.
But, in the above-described apparatus for controlling laser diode power, during the laser diode is controllable when the power level value is constant, such as reading. However, the laser diode is not controllable across three power levels such as reading, peak and bias power levels, such as are required for recording information onto the optical media.
Therefore, it is an object of the present invention to provide an apparatus and method for controlling power of a laser diode used in conjunction with an for optical recording media in which a diode power is controlled in parallel to independently control each of the power levels required for recording onto an optical recording medium so that laser diode power can be stably controlled with respect to both reading information from and recording information onto the optical recording medium.
To solve the above-mentioned object, according to the present invention, the apparatus and method for controlling power of the laser diode controls the power of a laser diode stably with respect to both reading from and recording onto the optical recording media by controlling the diode power in parallel to independently control each power level required for recording onto the optical recording media, and, as such, is different from the prior art which controls only one laser diode power level.